A key challenge for modern chemistry is the production of mesoscopic complexity and hierarchical order to ultimately bridge the
gap between the molecular world and functional microdevices. As proof of concept, nature shows unambiguously that this approach can be
rewarding. In particular, natural biominerals such as nacre, bone, and tooth enamel, consist of ordinary nanoscale components, yet
assemble complex polycrystalline materials that are clearly superior to their synthetic counterparts. In this context, an exciting model
system for biomimetic crystallization is the assembly of biomorphs by the co-precipitation of silica and metal carbonates. Despite being
formed by purely inorganic processes, these structures show "life-like" morphologies such as twisted helices and cardioid leaves. At the
nanoscale, silica-carbonate biomorphs consist of crystalline nanorods that assemble hierarchical architectures reminiscent of natural
biominerals. In this research work, we improve the level of control over the growth process and quantitatively characterize the biomorph
structures beyond simple qualitative observations. We report the synthesis of silica-carbonate biomorphs in single-phase, gradient-free
solutions that differ markedly from the typical solution-gas or gel-solution setups. Our experimental approach reveals novel biomorph
structural motifs, reduces transients in the chemical conditions, and expands the upper pH limit for biomorph formation to over 12 where
silica is essentially soluble. Moreover, the single-phase approach significantly increases the duration of growth to assemble biomorph
networks that extend to several millimeters. These unusually long biomorphs allow the first quantitative measurements of mesoscopic
parameters such as the helix wavelength, period, width, and linear as well as tangential growth velocities. We find that the latter
quantities are system-specific and tightly conserved during many hours of growth. We also systematically characterize the biomorph sheets
and report the existence of an additional level of self-organization that creates oscillatory height variations along the sheet surface.
These topographic features take the form of either concentric rings or disordered, patchy patterns with a wavelength of approximately 6.5
μm that shows no pronounced dependence on the reactant concentrations. These undulations are accompanied by a systematic out-of-plane
displacement of the nanorods. Our results are discussed in the context of an earlier hypothesis that predicts pH oscillations near the
crystallization front. We further investigate the effect of inorganic dopants that influence the morphological, compositional, and
crystallographic properties of biomorphs. In the case of Pb²⁺ and Ag⁺ ions, biomorph growth is disrupted by the formation of competing
precipitates. Similarly, the addition of Ca²⁺, Mg²⁺, and Zn²⁺ induces the rapid crystallization of witherite or amorphous silica-carbonate
aggregates at enhanced growth rates. By comparison, the addition of strontium ions results in the assembly of classic biomorphs such as
cardioid sheets and helices. Another aspect of the project lies at the overlap between geochemistry, paleontology, and astrobiology. To
date, these fascinating biomorph microstructures have only been synthesized using model laboratory solutions. We report that mineral
self-assembly can be also obtained from natural alkaline silica-rich water deriving from serpentinization. Specifically, we obtain water
samples from the Ney springs in California and demonstrate the self-assembly of nanocrystalline biomorphs of barium carbonate and silica,
as well as the formation mesocrystals and crystal aggregates of calcium carbonate with complex biomimetic textures. Our results suggest
that silica-induced mineral self-assembly could have been a common phenomenon in alkaline environments of the early Earth and Earth-like
planets. Moreover, the structural complexity obtained from these simple crystallization reactions in the natural Ney water further blurs
the boundaries between geochemical and biological microscale morphologies that not too long ago were perceived as sharp and
well-defined. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of
the Doctor of Philosophy. / Fall Semester 2016. / November 17, 2016. / Biomimetics, Biomorph, Crystallization, Hierarchical, Self-organization, Silica / Includes bibliographical references. / Oliver Steinbock, Professor Directing Dissertation; Richard Bertram, University Representative;
Ken L. Knappenberger, Committee Member; Hedi Mattoussi, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_405615 |
| Contributors | Nakouzi, Elias (authoraut), Steinbock, Oliver (professor directing dissertation), Bertram, R. (Richard) (university representative), Knappenberger, Kenneth L. (committee member), Mattoussi, Hedi (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Chemistry and Biochemistry (degree granting departmentdgg) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource (147 pages), computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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